1. Technical Field
The present invention relates to a semiconductor memory apparatus, and more particularly, to a combo semiconductor memory apparatus usable for both mobile DRAMs and general-purpose DRAMs.
2. Related Art
In recent years, combo dynamic random access memories (DRAMs) usable for both mobile DRAMs and general-purpose DRAMS have been proposed to shorten the time required to develop semiconductor memory apparatuses and to appropriately respond to the changes in the semiconductor memory market. The combo DRAM is designed to be supplied with two types of external voltages of 1.8 V and 3.3 V.
Meanwhile, general semiconductor memory apparatuses, such as DRAM, need to be supplied with a high-level voltage VPP for enabling a word line, and the high-level voltage VPP is generated by an external voltage.
For example, when an external voltage VDD of 1.8 V is applied to a semiconductor memory apparatus, the semiconductor memory apparatus performs charge pumping on the external voltage VDD of 1.8 V to generate a high-level voltage VPP. When an external voltage VDD of 3.3 V is applied to a semiconductor memory apparatus, the semiconductor memory apparatus performs charge pumping on the external voltage VDD of 3.3 V and lowers the pumped potential to a target potential to generate a high-level voltage VPP.
Semiconductor memory apparatuses according to the related art are designed to perform charge pumping to generate an internal voltage, such as the high-level voltage VPP, regardless of the level of an external voltage that is input.
Now, a voltage in the range of 3.3 V to 3.5 V is generally used as the high-level voltage VPP. However, even when an external voltage VDD of 3.3V is applied, the semiconductor memory apparatuses perform charge pumping, which results in current and power consumption.